System and method for preventing moisture migration

ABSTRACT

A system and a method are described for maintaining a first pressure of a first portion of a building below a second pressure of a second portion of the building to prevent moisture from migrating from the first portion to the second portion. The system may include a pressure measuring system, an exhaust air mover, and a microcontroller. The pressure measuring system, e.g., a differential pressure sensor, may be selectively operable to calculate a pressure difference value between the second pressure and the first pressure. The exhaust air mover, e.g., a fan assembly, may be adjustable for selectively varying exhaust of air from the first portion to an exterior of the building. The microcontroller may be in communication with the pressure measuring system and the exhaust air mover to instruct the exhaust air mover to increase or decrease the exhaust of air to maintain the pressure difference at a positive setpoint.

CROSS-REFERENCE TO RELATED APPLICATIONS

The subject patent application claims priority to and all the benefits of U.S. Provisional Patent Application Ser. No. 60/597,129, which was filed on Nov. 11, 2005, the entire specification of which is expressly incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to climate control systems, and more particularly to a system and method for maintaining a first pressure of a first portion of a building below a second pressure of a second portion of the building to prevent moisture from migrating from the first portion to the second portion.

2. Description of the Related Art

Buildings, such as commercial and residential buildings, may include a first portion of the building which encloses an indoor pool. Traditionally the air of the first portion of the building is heated to create an atmosphere conducive to swimming in the indoor pool. The warm air of the first portion of the building absorbs moisture from the pool. Generally the first portion of the building is outfitted to be compatible with the moist air. For example, the first portion of the building may be tiled and the furnishings in the first portion of the building may be made of materials that are not affected by moisture, such as vinyl, plastic, and glass.

The building generally includes a second portion of the building that is not outfitted to be compatible with moist air. The second portion of the building may include several separate rooms or sub-portions. For example, a residential house may have a second portion including a living area and a hotel may have a second portion include guest rooms. In general, the second portion of the building may include moisture sensitive materials such as wood, plush furnishings, plaster, and drywall.

The first portion and the second portion of the building may be separated by walls, ceilings, floors, doors, windows, or a combination thereof. The doors and windows include seals, but air may still seep around the seals and migrate from the first portion of the building to the second portion of the building. The walls, the ceilings, and the floors are typically constructed of permeable materials such as drywall, wood, concrete, or the like such that air and moisture may permeate through the walls, the ceilings, and the floors. In addition, the first portion and the second portion may be joined by a ventilation duct such that air may migrate between the first portion and the second portion of the building. The moisture from the first portion of the building may migrate from the first portion of the building to the second portion of the building through the window and door seals, the walls, the ceilings, the floors, and the ventilation ducts.

Accordingly, there exists a need for a system for controlling the pressure of the first portion of the building relative to the second portion of the building. More specifically, there exists a need for a system for maintaining the first pressure of the first portion of the building below the second pressure of the second portion of the building such that the air from the first portion of the building does not migrate to the second portion of the building. Additionally, there is a need for a method of maintaining the first pressure below the second pressure such that air from the first portion does not migrate to the second portion.

SUMMARY OF THE INVENTION AND ADVANTAGES

The present invention includes a system for maintaining a first pressure of a first portion of a building below a second pressure of a second portion of the building. The system may include a pressure measuring system, an exhaust air mover, and a microcontroller. The pressure measuring system may be in fluid communication with the first portion of the building and the second portion of the building. The pressure measuring system may be selectively operable to calculate a pressure difference value between the second pressure and the first pressure. The exhaust air mover may be disposed between the first portion of the building and an exterior of the building. The exhaust air mover may be adjustable for selectively varying exhaust of air from the first portion to the exterior. The microcontroller may be in communication with the pressure measuring system and the exhaust air mover. The microcontroller includes memory. The memory may store a positive setpoint value and may store a pressure maintenance program code to compare the pressure difference value to the positive setpoint value and to instruct the exhaust air mover to increase the exhaust of air when the pressure difference value is below the positive setpoint value or decrease the exhaust of air when the pressure difference value is above the positive setpoint value.

The present invention also includes a method for preventing migration of moisture from the first portion of the building to the second portion of the building. The method includes calculating a pressure difference between the second pressure of the second portion and the first pressure of the first portion. The method further includes comparing the pressure difference to a positive setpoint and exhausting air from the first portion to an exterior when the pressure difference is below the positive setpoint to maintain the pressure difference at the positive setpoint to prevent moisture from migrating from the first portion to the second portion.

Accordingly, the exhaust air mover exhausts air from the first portion of the building to the exterior of the building thereby maintaining the pressure difference between the second portion and the first portion. Because the positive setpoint is positive, the first pressure is less than the second pressure. As such, air is prevented from migrating from the first portion to the second portion so that moisture in the air of the first portion is prevented from migrating from the first portion to the second portion.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is perspective view of a building in partial section with a system assembled in the building;

FIG. 2 is a cross-sectional view of a portion of the building and a fan assembly mounted to the building;

FIG. 3 is a schematic view of the system;

FIG. 4 is a schematic view of a first alternative embodiment of the system;

FIG. 5 is a perspective view of a building in partial section with second alternative embodiment of the system assembled in the building; and

FIG. 6 is a schematic view of a third alternative embodiment of the system.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views, a system is generally shown at 20 for maintaining a first pressure of a first portion 22 of a building 24 below a second pressure of a second portion 26 of the building. The building 24 may be, for example, a residential or commercial building 24. The system 20 maintains a pressure difference between the second pressure and the first pressure. Specifically, the system 20 maintains the pressure difference at a positive setpoint. As discussed below, the positive setpoint may be predetermined based upon requirements of the building 24. The positive setpoint is positive in magnitude such that the first pressure is maintained below the second pressure. The system 20 maintains the first pressure of the first portion 22 below the second pressure of the second portion 26 to prevent moisture-laden air from migrating from the first portion 22 to the second portion 26.

Specifically, as shown FIGS. 1 and 4, the first portion 22 of the building 24 may enclose an indoor swimming pool 28. In such a configuration, the indoor swimming pool 28 moistens the air of the first portion 22 of the building 24. The first portion 22 of the building 24 and the second portion 26 of the building 24 may be separated by a wall 30, doors 32, windows 34, floors, ceilings or a combination thereof. The doors 32 and windows 34 include seals, but air may still seep around the seals and migrate between the first portion 22 of the building 24 to the second portion 26 of the building 24. In addition, the first and second portions 22 of the building 24 may be joined by a ventilation duct such that air may travel between the first and second portions 22, 26 of the building 24 through the ventilation duct. It is advantageous to maintain the pressure of the first portions 22 of the building 24 below the pressure of the second portion 26 of the building 24 such that the moisture does not migrate from the first portion 22 of the building 24 to the second portion 26 of the building 24 through the walls 30, doors 32, windows 34, ceilings, floors and/or ventilation duct. It should be appreciated that the present invention is not limited to use with the first portion 22 enclosing the swimming pool but may be used in any scenario where the air of the first portion 22 of the building 24 is more humid than the air of the second portion 26 of the building 24.

The positive setpoint may be a pressure range including an upper boundary and a lower boundary. Preferably, the lower boundary is sufficiently high such that moisture is prevented from migrating between the first portion 22 of the building 24 to the second portion 26 of the building 24. Conversely, preferably the upper boundary is sufficiently low such that the pressure difference does not damage seals around the doors 32 and/or windows 34 of the first portion 22 of the building 24. Specifically, if the pressure difference is excessively high, the pressure difference will cause the seals around the doors 32 and/or windows 34 to permanently deform such that the seals no longer seal properly around the doors 32 and/or windows 34, respectively. For example, the positive setpoint may be in the range of about 1 to about 4 Pa. In other words, in such a configuration the upper boundary is about 4 Pa and the lower boundary is about 1 Pa. However, it should be appreciated that pressures below and/or above these values can also be used in the practice of the present invention.

As shown schematically in FIGS. 3, 4, and 6, the system 20 includes a pressure measuring system 38 for fluid communication with the first portion 22 of the building 24 and fluid communication with the second portion 26 of the building 24 to calculate a pressure difference value between the second pressure and the first pressure. The system 20 further includes an exhaust air mover 40 (e.g., see also FIGS. 1 and 2) for disposition between the first portion 22 of the building 24 and an exterior 42 (e.g., see also FIG. 2) of the building 24. The exhaust air mover 40 may be adjustable for selectively varying exhaust of air from the first portion 22 to the exterior 42.

The system 20 includes a microcontroller 44 in communication with the pressure measuring system 38 and the exhaust air mover 40. The microcontroller 44 includes a memory. The memory may store a positive setpoint value corresponding to the positive setpoint. The memory may store a pressure maintenance program code to compare the pressure difference value to the positive setpoint value and to instruct the exhaust air mover 40 to increase the exhaust of air when the pressure difference value is below the positive setpoint value and decrease the exhaust of air when the pressure difference value is above the positive setpoint value. The positive setpoint value may be pre-set to the memory at a factory. Alternatively, the positive setpoint may be manually entered at the building 24. The setpoint may be calibrated after the system 20 has been assembled in the building 24.

In the embodiment wherein the positive setpoint is a pressure range with an upper boundary and a lower boundary, the positive setpoint value may be a value range including an upper boundary value corresponding to the upper boundary and a lower boundary value corresponding to the lower boundary. In such a configuration, the memory may store the upper boundary value, the lower boundary value, and the pressure maintenance program code to instruct the exhaust air mover 40 to increase the exhaust of air when the pressure difference value is below the lower boundary value or to decrease the exhaust of air when the pressure difference value is above the upper boundary value.

The pressure measuring system 38 may include a pressure sensor 46 in communication with the microcontroller 44, a first tube in fluid communication between the first portion 22 of the building 24 and the pressure sensor 46, and a second tube in fluid communication between the second portion 26 of the building 24 and the pressure sensor 46. Specifically, the first tube may have an open end disposed in the first portion 22 of the building 24 and the second tube may have an open end disposed in the second portion 26 of the building 24. The pressure of the first portion 22 and the pressure of the second portion 26 may be communicated through the first tube and the second tube, respectively, to the pressure sensor 46. It should be appreciated that the system 20 may include additional pressure sensors 46 and the additional pressure sensors 46 may measure pressures or pressure differences of separate zones or additional portions of the building 24.

As shown schematically in FIG. 4, the pressure sensor 46 may be a differential pressure sensor 50. In such a configuration, the first tube and the second tube may extend from the differential pressure sensor 50 to the first portion 22 and the second portion 26, respectively. The differential pressure sensor 50 may measure the pressure difference value corresponding to the pressure difference between the first pressure and the second pressure. The differential pressure sensor 50 may communicate the pressure difference value to the microcontroller 44.

For example, the differential pressure sensor 50 may convert the pressure difference into an analog signal. The differential pressure sensor 50 may communicate the analog signal to an analog-to-digital converter 51, which may convert the analog signal into a digital signal. The digital signal may be communicated from the analog-to-digital converter 51 to the microcontroller 44. It should be appreciated that the analog-to-digital converter 51 may be built into the microcontroller 44 and that the analog-to-digital converter 51 may not be necessary if the differential pressure sensor 50 is of a type that converts the pressure into the digital signal.

Alternatively, the pressure sensor 46 may be further defined as a first pressure sensor and a second pressure sensor each in communication with the microcontroller 44. In such a configuration, the first tube may extend from the first pressure sensor to the first portion 22 of the building 24 and the second tube may extend from the second pressure sensor to the second portion 26 of the building 24. The first pressure sensor may measure a first pressure value corresponding to the first pressure and the second pressure sensor may measure a second pressure value corresponding to the second pressure. The first and second pressure sensors may communicate the first and second pressure values, respectively, to the microcontroller 44 and the microcontroller 44 may use the first and second pressure values to calculate the pressure difference value.

For example, the first and second pressure sensors may convert the first and second pressures, respectively, into a first and a second analog signal. For example, the first and second pressure sensors may communicate the first and second analog signals, respectively, to the analog-to-digital converter 51, which may convert the first and second analog signals into a first and second digital signal. The first digital signal and the second digital signal may be communicated from the analog-to-digital converter 51 to the microcontroller 44. It should be appreciated that the analog-to-digital converter 51 may be built into the microcontroller 44 and the analog-to-digital converter 51 may not be necessary if the first and second pressure sensors are of a type that convert the first and second pressures, into the first digital signal and the second digital signal.

As shown in FIG. 2, the exhaust air mover 40 may be further defined as a fan assembly 52. The fan assembly 52 may include a conduit 54 for extension between the first portion 22 and the exterior 42, and a fan 56 disposed in the conduit 54 for moving air through the conduit 54 from the first portion 22 to the exterior 42. The fan assembly 52 may include a baffle 58 moveably positioned in the conduit 54 for selectively restricting air flow of the exhaust air exhausted through the conduit 54 by the fan 56. In other words, the baffle 58 may be moveable in the conduit 54 to effectively change the cross-sectional area of the conduit 54 to restrict the air flow.

As shown in FIGS. 1, 2, and 5, the fan assembly 52 may be mounted in an exterior wall 36 of the building 24 or in the ceiling 37 of the building 24. However, it should be appreciated that the fan assembly 52 may not be required to be mounted in the exterior wall 36 or the ceiling 37, but may be mounted anywhere in the first portion 22 of the building 24 such that fan assembly 52 exhausts air from the first portion 22 of the building 24 to the exterior 42.

The fan 56 may be switchable between an “on” mode and an “off” mode, wherein the fan 56 operates at a constant speed in the “on” mode. In such a configuration, the fan 56 may be switched to the on mode when the pressure difference is not at the positive setpoint and the fan 56 may be switched to the off mode when the pressure difference is at the positive setpoint. Alternatively, the fan 56 may operate in a variable speed mode, wherein the speed of the fan 56 is decreased as the pressure difference approaches the positive setpoint and wherein the speed of the fan 56 is increased as the pressure difference departs from the positive setpoint. In an embodiment wherein the positive setpoint is further defined as the pressure range, the speed of the fan 56 may be increased or decreased when the pressure difference is below or above, respectively, of a median of the pressure range.

The exhaust air mover 40 may include a control device 60 in communication with the microcontroller 44 for connection to a power source 62 to selectively vary an amount of electricity supplied to the exhaust air mover 40 from the power source 62. For example, the control device 60 may include a servomotor 64 and a rheostat 66. The servomotor 64 may include a servomotor shaft (not shown) extending from the servomotor 64 and the servomotor 64 may change the rotational angle of the servomotor shaft depending upon an output signal supplied to the servomotor 64 from the microcontroller 44.

The rheostat 66 may include a rheostat shaft (not shown). A clutch (not shown) may be engaged with the servomotor 64 shaft and with the rheostat shaft such that rotation of the servomotor 64 shaft is transferred to the rheostat shaft. The rheostat 66 may communicate with the exhaust air mover 40 to increase or decrease the flow of exhaust from the first portion 22 to the exterior 42.

For example, the rheostat 66 may communicate with the fan 56 to increase or decrease the rotational speed of the fan 56. In such a configuration, the rheostat 66 may be connected to the fan 56 with an electrical wire. Electrical power may be supplied through the rheostat 66 to the fan 56 and the amount of voltage supplied through the rheostat 66 to the fan 56 depends upon the rotational position of the rheostat 66 shaft. Changing the rotational angle of the rheostat shaft may increase or decrease the electrical voltage supplied through the rheostat 66 to the fan 56. A change in the output signal may change the rotational angle of the servomotor shaft, which in turn changes the rotational angle of the rheostat shaft, thereby changing the rotational speed of the fan 56. It should be appreciated that the pressure controller may include additional fans 56 in communication with the rheostat 66 such that a change in the output signal may result in a change in the rotational speed of the additional fans 56 to maintain the actual pressure difference between the first portion 22 and the second portion 26 of the building 24.

The rheostat shaft may rotate between a minimum rotational angle and a maximum rotational angle. The rheostat shaft is mechanically prevented from rotating beyond the minimum rotational angle or beyond the maximum rotational angle. Preferably, the servomotor 64 shaft and the rheostat shaft are generally equal in diameter and the clutch is a rubber tube that is press fit onto the servomotor 64 shaft and the rheostat shaft such that the servomotor 64 shaft rotates the clutch, which in turn rotates the rheostat shaft. If the rheostat shaft has been turned to the maximum position, the servomotor 64 shaft may rotate relative to the clutch. In other words, when the rheostat shaft has been rotated to the maximum position, the servomotor 64 shaft may slip within the clutch such that the rotation of the servomotor 64 is not transferred to the rheostat shaft.

It should be appreciated that the control device 60 may be any type of control device without departing from the nature of the present invention. For example, the control device 60 may include the rheostat, the servomotor, a variable speed fan controller, a potentiometer device, a stepper motor, or any combination thereof.

The memory of the microcontroller 44 may store a time limit value. In such a configuration, the system 20 may include a warning device 68 in communication with the microcontroller 44 for generating a warning when the pressure difference value remains below the positive setpoint value for a period of time exceeding the time limit value. For example, the warning device 68 may be an audible alarm generator and may generate audible beeps or a buzzer. For example, the warning device 68 may communicate with an alarm system 20 of the building 24.

As shown schematically in FIG. 4, the system 20 may include an electrical switch 70 connected to the exhaust air mover 40 for connection to the power source 62 and for disposition on an interior door 72 disposed in an opening between the first and second portions 22. In such a configuration, the electrical switch 70 may allow electricity to flow from the power source 62 to the exhaust air mover 40 when the interior door 72 is in an open position. In other words, when the interior door 72 is opened, the first pressure of the first portion 22 and the second pressure of the second portion 26 try to equilibrate through the open interior door 72. The opening of the interior door 72 activates the switch 70 and the switch 70 communicates with the exhaust air mover 40 such that power may be supplied to the exhaust air mover 40. Alternatively, the switch 70 may communicate with the rheostat 66 such that the maximum voltage may be supplied to the fan 56 to immediately compensate for the increasing pressure caused by the open door 32.

Alternatively, the system 20 may include an auxiliary exhaust air mover 74 disposed in the first portion 22 of the building 24 with the switch 70 in communication with the auxiliary exhaust air mover 74. The second exhaust fan 56 may exhaust air from the first portion 22 of the building 24 to the exterior 42 of the building 24. When the interior door 72 is in the open position, the first pressure of the first portion 22 and the second pressure of the second portion 26 try to equilibrate through the open interior door 72. The opening of the interior door 72 activates the switch 70 and the switch 70 communicates with the auxiliary exhaust air mover 74 such that power may be supplied to the auxiliary exhaust air mover 74. The auxiliary exhaust air mover 74 operates in addition to the exhaust fan 56 to compensate for the increasing pressure created by the open interior door 72.

As shown in FIG. 5, the building 24 may include a third portion 48 having a third pressure. For example, the third portion 48 may be separated from the first portion 22 by walls 30, windows 34, doors 32, ceilings, floors or a combination thereof. Additionally, the third portion 48 may be separated from the second portion 26 by walls 30, windows 34, doors 32, or a combination thereof. In such a configuration, the system 20 may maintain the first pressure below the third pressure. Because the first pressure may be maintained below both the second and third pressures, both the second and third pressures attempt to equilibrate with the first pressure. Depending upon the configuration of the second and third portions 26, 48, respectively, the second and third pressure may be different from each other. For example, the second and third pressures may be different due to bathroom exhaust fans, kitchen exhaust fans, range exhaust fans, an imbalance in return and supply air from a furnace, or a combination thereof.

Preferably, the second and third pressures are maintained within an equilibrium range. As shown schematically in FIG. 6, the system 20 may include an interior pressure measuring system 39 for fluid communication with the second and third portions 26, 48, respectively, of the building 24 to calculate an interior pressure difference between the second and third portions 26, 48, respectively. The system 20 may include an interior air mover 78 for disposition between the second portion 26 of the building 24 and the third portion 48 of the building 24. The interior air mover 78 may be adjustable for selectively varying a rate of exhaust of air between the second portion 26 and the third portion 48. Specifically, the interior air mover 78 may be mounted to an interior wall 31. The interior air mover 78 may move air from the second portion 26 to the third portion 48 and may move air from the third portion 48 to the second portion 26. The interior air mover 78 may be, for example, a second fan assembly similar to the fan assembly 52 described above. The interior air mover 78 may include an interior control device 61. The interior control device 61 may be, for example, similar to the control device 60 of the exterior air mover 40.

The memory of the microcontroller 44 may store an equilibrium pressure value range corresponding to the equilibrium pressure range. The memory may store pressure equilibrium program code to instruct the interior air mover 78 to selectively vary a direction and a rate of air flow between the second portion 26 and the third portion 48.

The system 20 may generate an interior pressure difference value corresponding to the interior pressure difference. For example, the system 20 may include an interior differential pressure sensor 50 in fluid communication with the second and third portions 26, 48, respectively. Alternatively, for example, the system 20 may include a pair of pressure sensors 46 with one of the pair in fluid communication with the first portion 22 and another of the pair in fluid communication with the second portion 26.

Specifically, the microcontroller 44 may execute the pressure equilibrium program code to instruct the interior air mover 78 to exhaust air from the second portion 26 to the third portion 48 when the interior pressure difference value is outside of the equilibrium pressure value range and the second pressure measurement is greater than the third pressure measurement. Additionally, the microcontroller 44 may execute the pressure equilibrium program to instruct the interior air mover 78 to exhaust air from the third portion 48 to the second portion 26 when the interior pressure difference value is outside of the equilibrium pressure value range and the third pressure measurement is greater than the second pressure measurement.

The system 20 may include a visible indicator that indicates whether power is being supplied to the exhaust air mover 40. For example, the visible indicator may include a first light emitting diode (LED) and a second LED. When no power is supplied to the exhaust air mover 40, the first LED may be illuminated and when power is supplied to the exhaust air mover 40 the second LED may be illuminated. The first LED and the second LED may, for example, be different colors. For example, the first LED may be red and the second LED may be green. Alternatively, the visible indicator may include a liquid crystal display (LCD). The LCD may, for example, display a message indicating whether power is being supplied to the exhaust air mover 40. The LCD may also display other messages.

For example, as shown in FIG. 1, the microcontroller 44 and the pressure measuring system 38 may be enclosed by a box 80. The box 80 may be disposed in a mechanical room 82 of the building 24. The warning device 68 and/or the visual indicator may be incorporated into the box 80. Alternatively, the warning device 68 and/or the visual indicator may be disposed in the first portion of the building.

The invention further includes a method of preventing migration of moisture from the indoor pool enclosed by the first portion 22 of the building 24 to the second portion 26 of the building 24. The method includes calculating a pressure difference between the second pressure of the second portion 26 and the first pressure of the first portion 22 and comparing the pressure difference to the positive setpoint. The method further includes exhausting air from the first portion 22 to the exterior 42 when the pressure difference is below the positive setpoint to maintain the pressure difference at the positive setpoint to prevent moisture-laden air from migrating from the first portion 22 of the building 24 to the second portion 26 of the building 24.

Exhausting air from the first portion 22 to the exterior 42 includes instructing the exhaust air mover 40 to exhaust air from the first portion 22 to the exterior 42. Exhausting air from the first portion 22 to the exterior 42 further includes instructing the exhaust air mover 40 to refrain from exhausting air from the first portion 22 to the exterior 42 when the pressure difference is above the positive setpoint.

Specifically, the method may include executing the pressure maintenance program code to compare the pressure difference value to the positive setpoint value and to communicate instructions from the microcontroller 44 to the exhaust air mover 40. More specifically, the method further includes communicating instructions from the microcontroller 44 to the exhaust air mover 40. Exhausting air from the first portion 22 to the exterior 42 portion includes instructing the exhaust air mover 40 to exhaust air from the first portion 22 to the exterior 42 when the pressure difference value is below the positive setpoint value and instructing the exhaust air mover 40 to refrain from exhausting air from the first portion 22 to the exterior 42 when the pressure difference value is above the positive setpoint value.

Exhausting air from the first portion 22 may include activating the fan 56 to move air through the conduit 54 from the first portion 22 to the exterior 42. In such a configuration, the microcontroller 44 communicates instructions to the fan assembly 52 to activate the fan 56. Exhausting air may also include adjusting a position of the baffle 58 in the conduit 54 to selectively restrict flow of air exhausted through the conduit 54 by the fan 56. In such a configuration, the microcontroller 44 may communicate instructions to the fan assembly 52 to adjust the baffle 58.

Instructing the exhaust air mover 40 may include instructing the control device 60 to selectively vary an amount of electricity supplied to the exhaust air mover 40 from the power source 62. An increase in the supply of electricity to the exhaust air mover 40 may increase the speed of the exhaust air mover 40, which may increase the exhaust of air from the first portion 22 to the exterior 42. Likewise, a decrease in the supply of electricity to the exhaust air mover 40 may decrease the speed of the exhaust air mover 40, which may decrease the exhaust of air from the first portion 22 to the exterior 42. Specifically, the method includes communicating instructions from the microcontroller 44 to the control device 60. More specifically, the method includes communicating instructions from the microcontroller 44 to the control device 60 to increase the amount of electricity supplied to the exhaust air mover 40 when the pressure difference value is below the positive setpoint. The method also includes communicating instructions to the control device 60 to decrease the amount of electricity supplied to the exhaust air mover 40 when the pressure difference value is above the positive setpoint.

Alternatively, the control device 60 may include a variable frequency drive. The variable frequency drive is connected to a power source and is in communication with the microcontroller 44 and with the exhaust air mover 40. The variable frequency drive varies the frequency of electricity supplied from the power source to the exhaust air mover 40. The variable frequency drive may be advantageous in use with an AC motor of the exhaust air mover 40 to prevent the AC motor from overheating. In such a configuration, the method may include communicating instructions from the microcontroller 44 to the variable frequency drive. More specifically, the method includes communicating instructions from the microcontroller 44 to the variable frequency drive to vary the frequency of the electricity supplied from the power source to the exhaust air mover 40 when the pressure difference value is above or below the positive setpoint.

In an embodiment wherein the positive setpoint is a range of pressures including the upper boundary and the lower boundary, the method includes instructing the exhaust air mover 40 to exhaust air from the first portion 22 to the exterior 42 when the pressure difference is below the lower boundary. The method may include instructing the exhaust air mover 40 to refrain from exhausting air from the first portion 22 to the exterior 42 when the pressure difference is above the upper boundary.

Determining the pressure difference includes comparing the first pressure and the second pressure to calculate the pressure difference value corresponding to the pressure difference. As discussed above, the pressure sensor 46 may be a differential pressure sensor 50 wherein the differential pressure sensor 50 calculates the pressure difference value. Alternatively, the pressure sensor 46 may include a second pressure sensor 46 and a first pressure sensor 46 wherein the microcontroller 44 calculates the pressure difference value.

The method may further include activating the warning device 68 when the pressure difference remains below the positive setpoint for a period of time exceeding the time limit value. As discussed above, the warning device 68 may be an audible warning generator. Activating the warning device 68 may further include supplying electricity to the audible warning generator to generate the audible warning.

The method may further include storing a log of a plurality of pressure difference values to the memory of the microcontroller 44. Specifically, the system 20 may include a pressure data logger. The microcontroller 44 may be further defined as the pressure data logger. In such a configuration, the microcontroller 44 stores the log on the memory of the microcontroller. Alternatively, the microcontroller 44 may include an external data logger, i.e., a component in communication with a main body of the microcontroller 44. In such a configuration, the external data logger stores the log on the memory of the external data logger.

For example, the log may be transferred from the memory to a personal computer. The personal computer may be programmed with software to read the pressure difference values. The microcontroller may store the log on a removeable memory. For example, the removeable memory may be a USB flash drive and the pressure difference values may be recorded to the USB flash drive. The removeable memory may be removed from the microcontroller 44 and may be plugged into a personal computer such that the log may be viewed on the personal computer. Alternatively, a serial adapter may be plugged into a port on the microcontroller 44 and a port on a personal computer. In such a configuration, the personal computer may be a laptop computer. The serial adapter may include a USB plug for connection to a USB port on the personal computer. In another embodiment, the microcontroller 44 may be in communication with a visual interface for displaying the log of pressure difference values. For example, the visual interface may be an LCD screen.

In an embodiment wherein the building 24 includes the third portion 48, the method further includes maintaining the interior pressure difference between the third pressure of the third portion 48 of the building 24 and the second pressure of the second portion 26 of the building 24 in the equilibrium pressure range. Maintaining the second pressure and the third pressure at the equilibrium pressure range may include instructing the interior air mover 78 to selectively vary a rate of exhaust of air between the second portion 26 and the third portion 48. Specifically, the method may include executing the equilibrium program code to compare the interior pressure difference value to the equilibrium pressure range value and to communicate instructions from the microcontroller 44 to the interior air mover 78.

The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Obviously, many modifications and variations of the present invention are possible in light of the above teachings, and the invention may be practiced otherwise than as specifically described. 

1. A method for preventing migration of moisture from a first portion of a building to a second portion of a building comprising: calculating a pressure difference between the second pressure of the second portion and the first pressure of the first portion; comparing the pressure difference to a positive setpoint; and exhausting air from the first portion to an exterior when the pressure difference is below the positive setpoint to maintain the pressure difference at the positive setpoint to prevent moisture from migrating from the first portion to the second portion.
 2. The method as set forth in claim 1, including further providing an exhaust air mover, wherein exhausting air from the first portion to the exterior includes instructing the exhaust air mover to exhaust air from the first portion to the exterior.
 3. The method as set forth in claim 2, wherein exhausting air from the first portion to the exterior includes instructing the exhaust air mover to refrain from exhausting air from the first portion to the exterior when the pressure difference is above the positive setpoint.
 4. The method as set forth in claim 2, wherein the exhaust air mover is further defined as a fan assembly having a conduit extending between the first portion and the exterior and a fan disposed in the conduit, wherein exhausting air from the first portion includes activating the fan to move air through the conduit from the first portion to the exterior.
 5. The method as set forth in claim 4, wherein the fan assembly includes a baffle moveably positioned in the conduit, wherein exhausting air includes adjusting a position of the baffle in the conduit to selectively restrict flow of air exhausted through the conduit by the fan.
 6. The method as set forth in claim 2, wherein the exhaust air mover includes a control device connected to a power source, wherein instructing the exhaust air mover includes instructing the control device to selectively vary an amount of electricity supplied to the exhaust air mover from the power source.
 7. The method as set forth in claim 2, including further providing a microcontroller in communication with the exhaust air mover, wherein determining the pressure difference includes comparing the first pressure and the second pressure to calculate a pressure difference value corresponding to the pressure difference.
 8. The method as set forth in claim 7, wherein the microcontroller includes a memory and the memory stores a positive setpoint value corresponding to the positive setpoint, wherein exhausting air from the first portion to the exterior includes instructing the exhaust air mover to exhaust air from the first portion to the exterior when the pressure difference value is below the positive setpoint value and instructing the exhaust air mover to refrain from exhausting air from the first portion to the exterior when the pressure difference value is above the positive setpoint value.
 9. The method as set forth in claim 7, including further providing a warning device in communication with the microcontroller, wherein the microcontroller includes a memory and the memory stores a time limit value corresponding to a predetermined time period and further including activating the warning device when the pressure difference remains above or below the positive setpoint for a period of time exceeding the time limit value.
 10. The method as set forth in claim 7, wherein the microcontroller includes a memory and further including storing a log of a plurality of pressure difference values to the memory.
 11. The method as set forth in claim 1, wherein the positive setpoint is a pressure range including an upper boundary and a lower boundary, wherein exhausting air from the first portion to the exterior includes instructing the exhaust air mover to exhaust air from the first portion to the exterior when the pressure difference is below the lower boundary and instructing the exhaust air mover to refrain from exhausting air from the first portion to the exterior when the pressure difference is above the upper boundary.
 12. The method as set forth in claim 1, including maintaining an interior pressure difference between a third pressure of a third portion of the building and the second pressure of the second portion of the building in an equilibrium pressure range.
 13. The method as set forth in claim 12, including further providing an interior air mover, wherein maintaining the second pressure and the third pressure at the equilibrium pressure range includes instructing the interior air mover to selectively vary a rate of exhaust of air between the second portion and the third portion.
 14. A system for maintaining a first pressure of a first portion of a building below a second pressure of a second portion of the building, said system comprising: a pressure measuring system in fluid communication with the first portion of the building and the second portion of the building being selectively operable to calculate a pressure difference value between the second pressure and the first pressure; an exhaust air mover for disposition between the first portion of the building and an exterior of the building, said exhaust air mover being adjustable for selectively varying exhaust of air from the first portion to the exterior; and a microcontroller in communication with said pressure measuring system and said exhaust air mover; said microcontroller having a memory with said memory storing a positive setpoint value and storing a pressure maintenance program code to compare the pressure difference value to the positive setpoint value and to instruct said exhaust air mover to increase the exhaust of air when the pressure difference value is below said positive setpoint value or decrease the exhaust of air when the pressure difference value is above said positive setpoint value.
 15. The system as set forth in claim 14, wherein said positive setpoint value is a value range including an upper boundary value and a lower boundary value, wherein said memory stores said upper boundary value, said lower boundary value, and said pressure maintenance program code to instruct said exhaust air mover to increase the exhaust of air when the pressure difference value is below said lower boundary value or to decrease the exhaust of air when the pressure difference value is above said upper boundary value.
 16. The system as set forth in claim 14, wherein said exhaust air mover is further defined as a fan assembly including a conduit for extension between the first portion and the exterior and a fan disposed in said conduit for moving air through said conduit from the first portion to the exterior.
 17. The system as set forth in claim 16, wherein said fan assembly includes a baffle moveably positioned in said conduit for selectively restricting air flow of the exhaust air exhausted through the conduit by said fan.
 18. The system as set forth in claim 14, wherein said exhaust air mover includes a control device in communication with said microcontroller for connection to a power source to selectively vary an amount of electricity supplied to the exhaust air mover from the power source.
 19. The system as set forth in claim 14, wherein said memory of said microcontroller stores a time limit value and further including a warning device in communication with said microcontroller for generating a warning when the pressure difference value remains above or below said positive setpoint value for a period of time exceeding said time limit value.
 20. The system as set forth in claim 19, wherein said warning device is further defined as an audible alarm generator.
 21. The system as set forth in claim 14, further including an electrical switch connected to said exhaust air mover for connection to a power source and for disposition on a door disposed in an opening between the first and second portions to allow electricity to flow from the power source to said exhaust air mover when the door is in an open position.
 22. The system as set forth in claim 14, further including an interior pressure measuring system for fluid communication with the second portion and a third portion of the building to calculate an interior pressure difference between the second and third portions.
 23. The system as set forth in claim 22, further including an interior air mover for disposition between the second portion and the third portion, said interior air mover being adjustable for selectively varying a rate of exhaust of air between the second portion and the third portion.
 24. The system as set forth in claim 23, wherein said memory of said microcontroller stores an equilibrium pressure range value and stores a pressure equilibrium program code to instruct said interior air mover to selectively vary a direction and a rate of air flow between the second portion and the third portion.
 25. The system as set forth in claim 14, wherein said pressure measuring system is further defined as a differential pressure sensor.
 26. The system as set forth in claim 14, wherein said pressure difference measuring device is further defined as a second pressure sensor and a first pressure sensor. 